Platelet extracellular vesicles and their mitochondrial content significantly improve survival and cytokine levels when transfused into mice with sepsis or H1N1 infections

BACKGROUNDMitochondrial transplantation has recently gained prominence as a novel technique primarily focused on addressing ischemiareperfusion injuries and rare mitochondrial mutation diseases. Platelets, abundant in the bloodstream, play a crucial role in immune function. Upon activation, platelets release mitochondria encapsulated within extracellular vesicles, here referred to as "mitlets". These mitlets exhibit a preference for being internalized by immune cells circulating in the bloodstream, enhancing their cellular energetics. Herein, we hypothesized that the transplantation of mitlets between young animals and aged animals may exert a significant influence on the progression of infectious diseases. STUDY DESIGN AND METHODSIn this study, murine models of Influenza H1N1 infection and sepsis were employed to investigate disease dynamics. Specifically, mitlets isolated from young and healthy mice were transplanted into cohorts of mice of the same age afflicted by H1N1 infection, or into aged mice subjected to polymicrobial infection and sepsis. Survival outcomes and the quantification of cytokine levels were assessed across experimental groups to elucidate the potential therapeutic effects of mitlet transplantation. RESULTSIn the matched-age H1N1 infection model, as predicted, mitlet transplantation did not yield a statistically significant improvement in survival, although it did show a trend towards a reduction in the circulating inflammatory cytokine burden. In the young-to-old sepsis model, the transplantation of mitlets was associated with a significant enhancement in survival rates and a substantial reduction in bacterial loads and circulating cytokine levels. DISCUSSIONOur findings suggest that mitochondrial transplantation may constitute a safe and promising avenue for enhancing the immune systems capacity to counter infectious threats. This pilot investigation sets the stage for further exploration. It is plausible that in the future, immune senescence resulting from diminished mitochondrial energy production could be ameliorated through such transplantation interventions. As a consequence, this approach holds substantial potential as a novel immunotherapeutic strategy for the management of infectious diseases.